Communication method, apparatus, and system

ABSTRACT

Embodiments of the present invention disclose a communication method, an apparatus, and a system. The communication method includes: receiving, by a terminal device, a context identifier sent by a second radio access network device, and sending, to a first radio access network device, a first message that includes the context identifier; receiving, by a core network device, a second message sent by the first radio access network device, and sending, to the second radio access network device, a message that includes the context identifier; and receiving, by the core network device, context information of the terminal device that is sent by the second radio access network device, and sending the context information to the first radio access network device. Therefore, communication between the first radio access network device and the second radio access network device is ensured, and working efficiency is improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2016/095030, filed on Aug. 12, 2016, the disclosure of which ishereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to wireless communications technologies,and in particular, to a communication method in a wireless network, anapparatus, and a system.

BACKGROUND

A light connection technology is being discussed in the 3rd GenerationPartnership Project (3GPP) specifications. A terminal device may enter alight connection mode under an instruction of a radio access network(RAN) device. The radio access network device is referred to as ananchor radio access network device. The light connection mode is a statebetween a radio resource control (RRC) connected mode and an RRC idlemode.

The terminal device that enters a light connection mode from an RRCconnected mode obtains a context identifier allocated by the anchorradio access network device. The terminal device and the anchor radioaccess network device each store connection-related context information.In addition, the terminal device may select, based on cell reselectionmobility, a cell to be camped on. The terminal device sends the contextidentifier to a serving radio access network device of the cell whenthere is a data transmission requirement. The serving radio accessnetwork device sends the context identifier to the anchor radio accessnetwork device, to obtain the context information of the terminal devicefrom the anchor radio access network device.

Generally, the foregoing communication process is implemented betweenthe anchor radio access network device and the serving radio accessnetwork device using a configured interface (for example, an X2interface). However, there may be no available interface between theanchor radio access network device and the serving radio access networkdevice. In this case, communication between the anchor radio accessnetwork device and the serving radio access network device cannot beimplemented.

SUMMARY

Embodiments of the present disclosure provide a communication method ina wireless network, an apparatus, and a system, to ensure effectivecommunication between an anchor radio access network device and aserving radio access network device, especially when there is noavailable interface between the anchor radio access network device andthe serving radio access network device, thereby improving workingefficiency of a system.

In the embodiments of the present disclosure, the serving radio accessnetwork device is a first radio access network device, and the anchorradio access network device is a second radio access network device.

According to an aspect, an embodiment of the present disclosure providesa communication method in a wireless network. The method includes:receiving, by a first radio access network device from a terminaldevice, a first message that includes a context identifier, where thecontext identifier includes an identifier of a second radio accessnetwork device and an identifier of the terminal device that isallocated by the second radio access network device; sending, by thefirst radio access network device, a second message to a core networkdevice, where the second message includes the context identifier; andreceiving, by the first radio access network device, context informationof the terminal device from the core network device, where the contextinformation of the terminal device is associated with the identifier ofthe terminal device. According to the communication method provided inthis embodiment, timely and effective communication can be ensured whenno available interface exists between the first radio access networkdevice and the second radio access network device, thereby improvingworking efficiency of a system.

In a possible design, the context identifier further includes publicland mobile network (PLMN) information corresponding to the second radioaccess network device and/or an area identifier corresponding to thesecond radio access network device.

In a possible design, the first message and the second message furtherinclude the PLMN information corresponding to the second radio accessnetwork device and/or the area identifier corresponding to the secondradio access network device.

According to the foregoing possible design, the core network device canaccurately determine the second radio access network device and send amessage, so that reliability of communication between the first radioaccess network device and the second radio access network device isimproved.

In a possible design, the first message further includes indicationinformation, and the indication information indicates that an areaidentifier corresponding to the first radio access network device isdifferent from the area identifier corresponding to the second radioaccess network device. The method further includes: sending, by thefirst radio access network device, an area identifier request message tothe terminal device; and receiving, by the first radio access networkdevice from the terminal device, the area identifier corresponding tothe second radio access network device. The second message furtherincludes the area identifier corresponding to the second radio accessnetwork device.

In a possible design, the method further includes: determining, by thefirst radio access network device based on the context identifier,whether additional information needs to be obtained, where theadditional information includes the PLMN information corresponding tothe second radio access network device and/or the area identifiercorresponding to the second radio access network device; if the firstradio access network device determines that the additional informationneeds to be obtained, sending, by the first radio access network device,an additional-information request message to the terminal device; andreceiving, by the first radio access network device, the additionalinformation from the terminal device. The second message furtherincludes the additional information.

According to the foregoing possible design, information carried in thefirst message can be simplified, a transmission resource occupied by thefirst message can be reduced, and transmission efficiency can beimproved.

In a possible design, the additional-information request message furtherincludes preamble allocation information, where the preamble allocationinformation is used to indicate a preamble allocated to the terminaldevice. The method further includes: receiving, by the first radioaccess network device, the preamble from the terminal device; sending,by the first radio access network device, an allocated transmissionresource to the terminal device; and receiving, by the first radioaccess network device from the terminal device, the additionalinformation sent by using the transmission resource.

In a possible design, the second message further includes an identifierof the first radio access network device.

In a possible design, the method further includes: receiving, by thefirst radio access network device, verification information from theterminal device. The second message further includes the verificationinformation and information about a serving cell in which the firstradio access network device serves the terminal device.

In a possible design, the sending, by the first radio access networkdevice, a second message to a core network device includes: determining,by the first radio access network device based on the identifier of thesecond radio access network device, whether an interface exists betweenthe first radio access network device and the second radio accessnetwork device; and if the interface does not exist, sending, by thefirst radio access network device, the second message to the corenetwork device.

According to another aspect, an embodiment of the present disclosureprovides a communication method in a wireless network. The methodincludes: sending, by a second radio access network device, a contextidentifier to a terminal device, where the context identifier includesan identifier of the second radio access network device and anidentifier of the terminal device that is allocated by the second radioaccess network device; receiving, by the second radio access networkdevice from a core network device, a message that includes the contextidentifier; and sending, by the second radio access network device,context information of the terminal device to the core network devicebased on the message that includes the context identifier, where thecontext information of the terminal device is associated with theidentifier of the terminal device. According to the communication methodprovided in this embodiment, timely and effective communication betweena first radio access network device and the second radio access networkdevice can be ensured, thereby improving working efficiency of a system.

In a possible design, the context identifier further includes PLMNinformation corresponding to the second radio access network deviceand/or an area identifier corresponding to the second radio accessnetwork device.

In a possible design, the message that is received by the second radioaccess network device from the core network device and that includes thecontext identifier further includes the PLMN information correspondingto the second radio access network device and/or the area identifiercorresponding to the second radio access network device.

In a possible design, the message that is received by the second radioaccess network device from the core network device and that includes thecontext identifier further includes at least one of an identifier of afirst radio access network device, PLMN information corresponding to thefirst radio access network device, and an area identifier correspondingto the first radio access network device. The first radio access networkdevice is a radio access network device that serves the terminal device.

In a possible design, the method further includes: receiving, by thesecond radio access network device from the core network device,verification information of the terminal device and information about aserving cell in which the first radio access network device serves theterminal device; and verifying, by the second radio access networkdevice, the terminal device based on the verification information andthe information about the serving cell.

In a possible design, before the receiving, by the second radio accessnetwork device from a core network device, a message that includes thecontext identifier, the method further includes: sending, by the secondradio access network device, control information to the terminal device,where the control information is used to instruct the terminal device toenter a light connection mode.

According to still another aspect, an embodiment of the presentdisclosure provides a communication method in a wireless network. Themethod includes: receiving, by a terminal device, a context identifierfrom a second radio access network device, where the context identifierincludes an identifier of the second radio access network device and anidentifier of the terminal device that is allocated by the second radioaccess network device; and sending, by the terminal device, a firstmessage to a first radio access network device, where the first messageincludes the context identifier.

In a possible design, the context identifier further includes PLMNinformation corresponding to the second radio access network deviceand/or an area identifier corresponding to the second radio accessnetwork device.

In a possible design, the first message further includes the PLMNinformation of the second radio access network device and/or the areaidentifier corresponding to the second radio access network device.

In a possible design, before the sending, by the terminal device, afirst message to a first radio access network device, the method furtherincludes: receiving, by the terminal device, the second area identifierof the second radio access network device; receiving, by the terminaldevice, a first area identifier of the first radio access networkdevice; and determining, by the terminal device, whether the second areaidentifier is the same as the first area identifier.

In a possible design, the first message further includes indicationinformation, where the indication information indicates that the firstarea identifier is different from the second area identifier.

In a possible design, the method further includes: receiving, by theterminal device, an area identifier request message sent by the firstradio access network device; and sending, by the terminal device, thesecond area identifier to the first radio access network device inresponse to the area identifier request message.

In a possible design, before the sending, by the terminal device, afirst message to a first radio access network device, the method furtherincludes: truncating, by the terminal device, the context identifieraccording to an instruction of the first radio access network device,where the first message includes a part of the context identifierobtained after the truncation.

In a possible design, after the sending, by the terminal device, a firstmessage to a first radio access network device, the method furtherincludes: receiving, by the terminal device, an additional-informationrequest message from the first radio access network device, whereadditional information includes at least one of the area identifiercorresponding to the second radio access network device, the PLMNinformation corresponding to the second radio access network device, andanother remaining part of the context identifier obtained after thetruncation; and sending, by the terminal device, the additionalinformation to the first radio access network device in response to theadditional-information request message.

In a possible design, the additional-information request message furtherincludes preamble allocation information, where the preamble allocationinformation is used to indicate a preamble allocated to the terminaldevice. The method further includes: sending, by the terminal device,the preamble to the first radio access network device; receiving, by theterminal device, transmission resource information from the first radioaccess network device, where the transmission resource informationindicates a transmission resource allocated by the first radio accessnetwork device to the terminal device; and sending, by the terminaldevice, the additional information to the first radio access networkdevice by using the transmission resource.

In a possible design, the method further includes: sending, by theterminal device, verification information of the terminal device to thefirst radio access network device.

According to yet another aspect, an embodiment of the present disclosureprovides a communication method in a wireless network. The methodincludes: receiving, by a first core network device, a second messagefrom a first radio access network device, where the second messageincludes a context identifier of a terminal device, and the contextidentifier includes an identifier of a second radio access networkdevice and an identifier of the terminal device that is allocated by thesecond radio access network device; sending, by the first core networkdevice, a third message to a second core network device or the secondradio access network device, where the third message includes thecontext identifier; receiving, by the first core network device, contextinformation of the terminal device from the second core network deviceor the second radio access network device, where the context informationis associated with the identifier of the terminal device; and sending,by the first core network device, the context information to the firstradio access network device. According to the communication methodprovided in this embodiment, a message between the first radio accessnetwork device and the second radio access network device can beforwarded by using a core network device, thereby ensuring timely andeffective communication.

In a possible design, the context identifier further includes PLMNinformation corresponding to the second radio access network deviceand/or an area identifier corresponding to the second radio accessnetwork device.

In a possible design, the second message and the third message furtherinclude the PLMN information corresponding to the second radio accessnetwork device and/or the area identifier corresponding to the secondradio access network device.

In a possible design, the second message and the third message furtherinclude verification information of the terminal device and informationabout a serving cell in which the first radio access network deviceserves the terminal device.

In a possible design, the second message further includes an identifierof the first radio access network device.

In a possible design, the third message further includes at least one ofthe identifier of the first radio access network device, PLMNinformation corresponding to the first radio access network device, andan area identifier corresponding to the first radio access networkdevice.

According to yet another aspect, an embodiment of the present disclosureprovides a communication method in a wireless network. The methodincludes: receiving, by a second core network device from a first radioaccess network device or a first core network device, a fourth messagethat includes a context identifier of a terminal device, where thecontext identifier includes an identifier of a second radio accessnetwork device and an identifier of the terminal device that isallocated by the second radio access network device; sending, by thesecond core network device to the second radio access network device, amessage that includes the context identifier; receiving, by the secondcore network device, context information of the terminal device from thesecond radio access network device, where the context information of theterminal device is associated with the identifier of the terminaldevice; and sending, by the second core network device, the contextinformation to the first radio access network device or the first corenetwork device. According to the communication method provided in thisembodiment, a message between the first radio access network device andthe second radio access network device can be forwarded by using a corenetwork device, thereby ensuring timely and effective communication.

In a possible design, the context identifier further includes PLMNinformation corresponding to the second radio access network deviceand/or an area identifier corresponding to the second radio accessnetwork device.

In a possible design, the fourth message and the message that includesthe context identifier further include the PLMN informationcorresponding to the second radio access network device and/or the areaidentifier corresponding to the second radio access network device.

In a possible design, the fourth message further includes an identifierof the first radio access network device.

In a possible design, the fourth message further includes verificationinformation and information about a serving cell in which the firstradio access network device serves the terminal device.

In a possible design, the message that includes the context identifierfurther includes at least one of the identifier of the first radioaccess network device, PLMN information corresponding to the first radioaccess network device, and an area identifier corresponding to the firstradio access network device, where the first radio access network deviceis an access network device that serves the terminal device.

In a possible design, the method further includes: sending, by thesecond core network device to the second radio access network device,the verification information of the terminal device and the informationabout the serving cell in which the first radio access network deviceserves the terminal device.

According to yet another aspect, an embodiment of the present disclosureprovides a radio access network device, and the radio access networkdevice has a function of implementing an action of the first radioaccess network device in the foregoing methods. The radio access networkdevice includes a receiver, a processor, and a transmitter. The receiveris configured to receive, from a terminal device, a first message thatincludes a context identifier. The processor is configured to decode thefirst message that includes the context identifier, where the contextidentifier includes an identifier of a second radio access networkdevice and an identifier of the terminal device that is allocated by thesecond radio access network device. The transmitter is configured tosend a second message to a core network device, where the second messageincludes the context identifier. The receiver is further configured toreceive context information of the terminal device from the core networkdevice, where the context information of the terminal device isassociated with the identifier of the terminal device.

In a possible design, the transmitter is further configured to send anarea identifier request message to the terminal device. The receiver isfurther configured to receive, from the terminal device, an areaidentifier corresponding to the second radio access network device. Thesecond message further includes the area identifier corresponding to thesecond radio access network device.

In a possible design, the processor is further configured to determine,based on the context identifier, whether additional information needs tobe obtained, where the additional information includes PLMN informationcorresponding to the second radio access network device and/or the areaidentifier corresponding to the second radio access network device. Ifthe processor determines that the additional information needs to beobtained, the transmitter is further configured to send anadditional-information request message to the terminal device. Thereceiver is further configured to receive the additional informationfrom the terminal device. The second message further includes theadditional information.

In a possible design, the additional-information request message furtherincludes preamble allocation information, where the preamble allocationinformation is used to indicate a preamble allocated to the terminaldevice. The receiver is further configured to receive the preamble fromthe terminal device. The processor is further configured to allocate atransmission resource to the terminal device. The transmitter is furtherconfigured to send the allocated transmission resource to the terminaldevice. The receiver receives, from the terminal device, the additionalinformation sent by using the transmission resource.

In a possible design, the receiver is further configured to receiveverification information from the terminal device. The second messagefurther includes the verification information and information about aserving cell in which the radio access network device serves theterminal device.

In a possible design, the processor is further configured to determine,based on the identifier of the second radio access network device,whether an interface exists between the radio access network device andthe second radio access network device. If the interface does not exist,the transmitter is configured to send the second message to the corenetwork device.

According to yet another aspect, an embodiment of the present disclosureprovides a radio access network device, and the radio access networkdevice has a function of implementing an action of the second radioaccess network device in the foregoing methods. The radio access networkdevice includes a processor, a transmitter, and a receiver. Theprocessor is configured to allocate an identifier of a terminal deviceto the terminal device. The transmitter is configured to send a contextidentifier to the terminal device, where the context identifier includesan identifier of the radio access network device and the identifier ofthe terminal device. The receiver is configured to receive, from a corenetwork device, a message that includes the context identifier. Theprocessor is further configured to determine context information of theterminal device in response to the message that includes the contextidentifier, where the context information of the terminal device isassociated with the identifier of the terminal device. The transmitteris further configured to send the context information of the terminaldevice to the core network device.

In a possible design, the receiver is further configured to receive,from the core network device, verification information of the terminaldevice and information about a serving cell in which a first radioaccess network device serves the terminal device. The processor isfurther configured to verify the terminal device based on theverification information and the information about the serving cell.

In a possible design, before the receiver receives, from the corenetwork device, the message that includes the context identifier, thetransmitter is further configured to send control information to theterminal device. The control information is used to instruct theterminal device to enter a light connection mode.

Functions of units in the radio access network devices in the foregoingaspects may be further implemented by executing corresponding softwareby hardware.

According to yet another aspect, an embodiment of the present disclosureprovides a terminal device, and the terminal device performs thecommunication method in a wireless network in the foregoing aspects. Theterminal device includes a receiver, a processor, and a transmitter. Thereceiver is configured to receive a context identifier from a secondradio access network device. The processor is configured to decode thecontext identifier, where the context identifier includes an identifierof the second radio access network device and an identifier of theterminal device that is allocated by the second radio access networkdevice. The transmitter is configured to send a first message to a firstradio access network device, where the first message includes thecontext identifier.

In a possible design, before the transmitter is configured to send thefirst message to the first radio access network device, the receiver isfurther configured to receive the second area identifier of the secondradio access network device and a first area identifier of the firstradio access network device. The processor is further configured todetermine whether the second area identifier is the same as the firstarea identifier.

In a possible design, the receiver is further configured to receive anarea identifier request message sent by the first radio access networkdevice. The processor is configured to: in response to the areaidentifier request message, control the transmitter to send the secondarea identifier to the first radio access network device.

In a possible design, the processor is further configured to truncatethe context identifier according to an instruction of the first radioaccess network device, where the first message includes a part of thecontext identifier obtained after the truncation.

In a possible design, the receiver is further configured to receive anadditional-information request message from the first radio accessnetwork device, where additional information includes at least one ofthe area identifier corresponding to the second radio access networkdevice, PLMN information corresponding to the second radio accessnetwork device, and another remaining part of the context identifierobtained after the truncation. The processor is further configured to:in response to the additional-information request message, control thetransmitter to send the additional information to the first radio accessnetwork device.

In a possible design, the processor is further configured to decode theadditional-information request message, where the additional-informationrequest message further includes preamble allocation information, andthe preamble allocation information is used to indicate a preambleallocated to the terminal device. The transmitter is further configuredto send the preamble to the first radio access network device. Thereceiver is further configured to receive transmission resourceinformation from the first radio access network device, where thetransmission resource information indicates a transmission resourceallocated by the first radio access network device to the terminaldevice. The transmitter is further configured to send the additionalinformation to the first radio access network device by using thetransmission resource.

In a possible design, the transmitter is further configured to sendverification information of the terminal device to the first radioaccess network device.

Functions of units in the terminal device may be further implemented byexecuting corresponding software by hardware.

According to yet another aspect, an embodiment of the present disclosureprovides a core network device, and the core network device has afunction of implementing an action of the first core network device inthe foregoing methods. The core network device includes a receiver, aprocessor, and a transmitter. The receiver is configured to receive asecond message from a first radio access network device. The processoris configured to decode the second message. The second message includesa context identifier of a terminal device. The context identifierincludes an identifier of a second radio access network device and anidentifier of the terminal device that is allocated by the second radioaccess network device. The transmitter is configured to send a thirdmessage to a second core network device or the second radio accessnetwork device, where the third message includes the context identifier.The receiver is further configured to receive context information of theterminal device from the second core network device or the second radioaccess network device, where the context information is associated withthe identifier of the terminal device. The transmitter is furtherconfigured to send the context information to the first radio accessnetwork device.

According to yet another aspect, an embodiment of the present disclosureprovides a core network device, and the core network device has afunction of implementing an action of the second core network device inthe foregoing methods. The core network device includes a receiver, aprocessor, and a transmitter. The receiver is configured to receive afourth message from a first radio access network device or a first corenetwork device. The processor is configured to decode the fourthmessage. The fourth message includes a context identifier of a terminaldevice, and the context identifier includes an identifier of a secondradio access network device and an identifier of the terminal devicethat is allocated by the second radio access network device. Thetransmitter is configured to send, to the second radio access networkdevice, a message that includes the context identifier. The receiver isfurther configured to receive context information of the terminal devicefrom the second radio access network device, where the contextinformation of the terminal device is associated with the identifier ofthe terminal device. The transmitter is further configured to send thecontext information to the first radio access network device or thefirst core network device.

In a possible design, the transmitter is further configured to send, tothe second radio access network device, verification information of theterminal device and information about a serving cell in which the firstradio access network device serves the terminal device.

Functions of units in the core network devices in the foregoing aspectsmay be further implemented by executing corresponding software byhardware.

According to yet another aspect, an embodiment of the present disclosureprovides a communications system, and the communications system includesthe radio access network device, the terminal device, and the corenetwork device described in the foregoing aspects.

According to yet another aspect, an embodiment of the present disclosureprovides a computer storage medium, configured to store a computersoftware instruction used by the foregoing radio access network device,and the computer software instruction includes a program designed forperforming the foregoing aspects.

According to yet another aspect, an embodiment of the present disclosureprovides a computer storage medium, configured to store a computersoftware instruction used by the foregoing terminal device, and thecomputer software instruction includes a program designed for performingthe foregoing aspects.

According to yet another aspect, an embodiment of the present disclosureprovides a computer storage medium, configured to store a computersoftware instruction used by the foregoing core network device, and thecomputer software instruction includes a program designed for performingthe foregoing aspects.

According to the technical solutions provided in the embodiments of thepresent disclosure, the first radio access network device and the secondradio access network device communicate with each other by using a corenetwork device, to ensure that communication can still be performed in atimely and effective manner when no available interface exists betweenthe first radio access network device and the second radio accessnetwork device, thereby improving working efficiency of a system.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentdisclosure more clearly, the following briefly introduces theaccompanying drawings required for describing the embodiments.Apparently, the accompanying drawings in the following description showmerely some embodiments of the present disclosure, and a person ofordinary skill in the art may still derive other accompanying drawingsfrom these accompanying drawings in a proper range.

FIG. 1A is a schematic diagram of a possible communications networkscenario according to an embodiment of the present disclosure;

FIG. 1B is a schematic diagram of another possible communicationsnetwork scenario according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of a communication method according to anembodiment of the present disclosure;

FIG. 3 is a schematic diagram of a communication method according toanother embodiment of the present disclosure;

FIG. 4 is a possible schematic structural diagram of a radio accessnetwork device according to an embodiment of the present disclosure;

FIG. 5 is another possible schematic structural diagram of a radioaccess network device according to an embodiment of the presentdisclosure;

FIG. 6 is another possible schematic structural diagram of a radioaccess network device according to an embodiment of the presentdisclosure;

FIG. 7 is another possible schematic structural diagram of a radioaccess network device according to an embodiment of the presentdisclosure;

FIG. 8 is a possible schematic structural diagram of a terminal deviceaccording to an embodiment of the present disclosure;

FIG. 9 is another possible schematic structural diagram of a terminaldevice according to an embodiment of the present disclosure;

FIG. 10 is a possible schematic structural diagram of a core networkdevice according to an embodiment of the present disclosure;

FIG. 11 is another possible schematic structural diagram of a corenetwork device according to an embodiment of the present disclosure;

FIG. 12 is another possible schematic structural diagram of a corenetwork device according to an embodiment of the present disclosure; and

FIG. 13 is another possible schematic structural diagram of a corenetwork device according to an embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

The technical solutions in the embodiments of the present disclosure areclearly described in the following with reference to the accompanyingdrawings. Apparently, the described embodiments are merely some but notall of the embodiments of the present disclosure. It may be understoodthat, without any ambiguity or contradiction, another embodimentobtained by a person of ordinary skill in the art by combining technicalfeatures in the embodiments or among the embodiments also falls withinthe protection scope of the present disclosure.

The solutions provided in the embodiments of the present disclosure arebased on a communications system 100 shown in FIG. 1A or FIG. 1B. Thecommunications system 100 includes at least one core network device, atleast two radio access network (RAN) devices, and at least one terminaldevice. Each radio access network device covers at least one cell. Theat least two radio access network devices include one anchor radioaccess network device and at least one serving radio access networkdevice. Each of the radio access network devices is connected to thecore network device by using a communications interface. Thecommunications interface may be an Si interface. The core network devicemay be a device that has a mobility management function.

The anchor radio access network device may instruct the terminal deviceto enter a light connection mode, and allocate a context identifier tothe terminal device. The light connection mode may be a sub-state of aradio resource control (RRC) connected mode, or may be an enhanced stateof an idle mode, or may be an independent state. The light connectionmode may also be referred to as an inactive state, a deactivated state,a low active state, a low overhead state, or the like. A form and a nameof the light connection mode are not specifically limited in theembodiments of the present disclosure. The terminal device that is in alight connection mode stores context information, and has mobility forperforming cell reselection.

Both the anchor radio access network device and the terminal device thatenters a light connection mode store context information of the terminaldevice. The context information may include a configuration parameter ofa connection between the anchor radio access network device and theterminal device.

If the terminal device that enters a light connection mode does notchange a camped cell, when the terminal device has a data transmissionrequirement, the terminal device may restore an RRC connection to theanchor radio access network device by using the stored contextinformation, thereby avoiding signaling overloads in an RRC connectionre-establishment process.

If the terminal device that enters a light connection mode changes acamped cell, the anchor radio access network device does not need togive a handover instruction, and the terminal device determines, basedon a cell reselection criterion, a cell to be camped on. For example,when finding a cell with better signal quality or higher signalstrength, the terminal device may select to camp on the cell. In thecell to be camped on, the terminal device is served by a serving radioaccess network device. When the terminal device has a data transmissionrequirement, the terminal device may establish an RRC connection to theserving radio access network device, to obtain a data transmissionservice provided by the serving radio access network device.

Specifically, as shown in FIG. 1A and FIG. 1B, the communications system100 includes a radio access network device 10, a radio access networkdevice 20, and a terminal device 30. The radio access network device 10is an anchor radio access network device, and the radio access networkdevice 20 is a serving radio access network device. The radio accessnetwork device 10 controls a cell A. The radio access network device 20controls a cell B. It may be understood that the radio access networkdevice 10 and the radio access network device 20 may control more cellsother than the cell A and the cell B. The terminal device 30 enters alight connection mode under an instruction of the radio access networkdevice 10. Afterwards, the terminal device 30 moves to the cell B. Inthe cell B, the radio access network device 20 provides a datatransmission service for the terminal device.

In the solutions of the embodiments of the present disclosure, there isa communications interface between the radio access network device 10and a core network device, and there is a communications interfacebetween the radio access network device 20 and the same core networkdevice. For example, the communications interface is an S1 interface.Therefore, both the radio access network device 10 and the radio accessnetwork device 20 may be controlled by the same core network device. Forexample, in the communications system 100 shown in FIG. 1A, there is acommunications interface between the radio access network device 10 anda core network device 1, and there is a communications interface betweenthe radio access network device 20 and the core network device 1.Therefore, both the radio access network device 10 and the radio accessnetwork device 20 may be controlled by the core network device 1.

In the solutions of the embodiments of the present disclosure, there maybe a communications interface between the radio access network device 10and one core network device, and there may be a communications interfacebetween the radio access network device 20 and another core networkdevice. Therefore, the radio access network device 10 and the radioaccess network device 20 are controlled separately by different corenetwork devices. For example, in the communications system 100 shown inFIG. 1B, there is a communications interface between the radio accessnetwork device 10 and a core network device 1, and there is acommunications interface between the radio access network device 20 anda core network device 2.

Generally, each core network device is responsible for managing at leastone mobility management area. For example, the mobility management areamay be a tracking area (TA), and each core network device iscorresponding to at least one tracking area. Each TA may becorresponding to a tracking area code (TAC), and the TAC may be used toidentify the corresponding TA. Certainly, the area may alternatively bea routing area (RA) corresponding to a routing area code (RAC), or alocation area (LA) corresponding to a location area code (LAC). The corenetwork device 1 may communicate with the core network device 2.

In the embodiments of the present disclosure, the communications system100 may be a global system for mobile communications (GSM), a codedivision multiple access (CDMA) system, a wideband code divisionmultiple access (WCDMA) system, a general packet radio service (GPRS), along term evolution (LTE) system, an LTE frequency division duplex (FDD)system, LTE time division duplex (TDD) system, a universal mobiletelecommunication system (UMTS), and another wireless communicationssystem in which an orthogonal frequency division multiplexing (OFDM)technology is used. A system architecture and a service scenario thatare described in the embodiments of the present disclosure are intendedto describe the technical solutions of the embodiments of the presentdisclosure more clearly, and constitute no limitation on the technicalsolutions provided in the embodiments of the present disclosure. Aperson of ordinary skill in the art may know that as networkarchitectures evolve and a new service scenario emerges, the technicalsolutions provided in the embodiments of the present disclosure are alsoapplicable to a similar technical problem.

In the embodiments of the present disclosure, the radio access networkdevice (for example, the radio access network devices 10 and 20) may beconfigured to provide a wireless communication function for the terminaldevice. The radio access network device may include a macro basestation, a micro base station (also referred to as a small cell), arelay station, an access point, and the like that are in various forms.The radio access network device may be a base transceiver station (BTS)in GSM or CDMA, a NodeB (NB) in WCDMA, an evolved NodeB (eNB or eNodeB)in LTE, or a corresponding next generation NodeB (gNB) in a 5G network.For ease of description, in all the embodiments of the presentdisclosure, the foregoing apparatuses that provide a wirelesscommunication function for the terminal device are collectively referredto as radio access network devices.

In the embodiments of the present disclosure, the terminal device (forexample, the terminal device 30) may also be referred to as userequipment (user equipment, UE), a mobile station (MS), a mobileterminal, or the like, and the terminal device may communicate with oneor more core networks by using a radio access network (RAN). Forexample, the terminal device may be a mobile phone (or referred to as a“cellular phone”), a computer with a mobile terminal, or the like. Forexample, the terminal device may alternatively be a portable,pocket-sized, handheld, computer built-in, or in-vehicle mobileapparatus, which exchanges voice and/or data with the radio accessnetwork. This is not specifically limited in the embodiments of thepresent disclosure.

In the embodiments of the present disclosure, the core network devicecontrols one or more radio access network devices, and may performcentralized management on resources in a system, or may configure aresource for the terminal device. For example, the radio access networkdevice may be a NodeB and a radio network controller (RNC) in the UMTS,and the core network device may be a serving GPRS support node (SGSN)and a gateway GPRS support node (GGSN). For another example, the radioaccess network device may be an eNB in the LTE system, and the corenetwork device may be a mobility management entity (MME). For anotherexample, the core network device may be a wireless network inter-RATcoordinating controller, or the like. This is not specifically limitedin the embodiments of the present disclosure.

It should be noted that a quantity of network elements included in thecommunications system 100 shown in FIG. 1A and FIG. 1B is merely anexample, and the embodiments of the present disclosure are not limitedthereto. In addition, although the core network devices 1 and 2, theradio access network devices 10 and 20, and the terminal device 30 areshown in the communications system 100 shown in FIG. 1A or FIG. 1B,network elements included the communications system 100 may not belimited to the foregoing network elements. For example, thecommunications system 100 may further include a device configured tocarry a virtualized network function. Details are not described herein.

When the terminal device needs to establish an RRC connection to theserving radio access network device, the serving radio access networkdevice may obtain the context information of the terminal device fromthe anchor radio access network device. Therefore, the serving radioaccess network device needs to communicate with the anchor radio accessnetwork device, to complete transfer of the context information.

Generally, an interface is configured between radio access networkdevices. Communication is implemented between the anchor radio accessnetwork device and the serving radio access network device by using aconfigured interface. However, due to reasons such as area division orlow power, no communications interface may be configured between radioaccess network devices, or an interface between radio access networkdevices may be unavailable. In this case, communication cannot beimplemented between the anchor radio access network device and theserving radio access network device. Consequently, the terminal devicecannot obtain a data transmission service in a timely manner after acell reselection, and working efficiency is reduced.

Based on the foregoing technical problem, according to a communicationmethod in a wireless network provided in the embodiments of the presentdisclosure, when communication cannot be directly performed between theanchor radio access network device and the serving radio access networkdevice by using an interface, message processing is performed accordingto the method in the embodiments of the present disclosure by using thecore network device, to ensure timely and effective informationobtaining and data transmission, thereby improving working efficiency.Certainly, based on the communication method in a wireless networkprovided in the embodiments of the present disclosure, regardless ofwhether a communications interface exists between the anchor radioaccess network device and the serving radio access network device, themethod provided in the embodiments of the present disclosure can beused, to implement process uniformity in different cases.

For ease of description and to avoid unnecessary restrictions, theserving radio access network device is referred to as a first radioaccess network device, and the anchor radio access network device isreferred to as a second radio access network device below.

FIG. 2 is a schematic diagram of a communication method in a wirelessnetwork according to an embodiment of the present disclosure. In thisembodiment, as shown in FIG. 1A, the first radio access network deviceand the second radio access network device are controlled by a same corenetwork device. The method provided in this embodiment is described indetail below from a perspective of interaction with reference to FIG. 2.

S201. The second radio access network device sends a context identifierto a terminal device.

The context identifier includes an identifier of the second radio accessnetwork device and an identifier of the terminal device that isallocated by the second radio access network device. The contextidentifier may be used to identify the terminal device, or may be usedto identify context information of the terminal device.

The context identifier may be an independent identifier that includescontinuous character strings. The context identifier may be used touniquely identify the terminal device within a local range, for example,uniquely identify the terminal device within a tracking area or a publicland mobile network (PLMN). The context identifier may also be used touniquely identify the terminal device globally.

The context identifier may include continuous character strings thatinclude the identifier of the second radio access network device and theidentifier of the terminal device. The context identifier mayalternatively include discontinuous character strings that include theidentifier of the second radio access network device and the identifierof the terminal device. The identifier of the second radio accessnetwork device that is included in the context identifier may include anidentifier of an area and an identifier of the second radio accessnetwork device in the area. This is not specifically limited in thisembodiment of the present disclosure.

Optionally, the context identifier further includes PLMN informationcorresponding to the second radio access network device and/or an areaidentifier corresponding to the second radio access network device. Thearea identifier may be a tracking area code (TAC), a routing area code(RAC), or a location area code (LAC). The PLMN information correspondingto the second radio access network device and/or the area identifiercorresponding to the second radio access network device are/is used todetermine globally a core network device corresponding to the secondradio access network device.

Optionally, the second radio access network device sends controlinformation to the terminal device, to instruct the terminal device toenter a light connection mode. The second radio access network deviceand the terminal device each store the context information of theterminal device. The context information of the terminal device isassociated with the identifier of the terminal device.

The context information may include a configuration parameter of aconnection between the second radio access network device and theterminal device. Specifically, the configuration parameter of aconnection may include a radio bearer configuration of the terminaldevice, and the radio bearer configuration includes a signaling radiobearer configuration and/or a data radio bearer configuration. Thecontext information may further include key information, and the keyinformation is used during encrypted transmission or during generationof verification information of the terminal device.

S202. The terminal device receives the context identifier from thesecond radio access network device, and sends, to a first radio accessnetwork device, a first message that includes the context identifier.

Specifically, the terminal device camps, based on cell reselection, on acell in which the first radio access network device provides a service.The terminal device may send, to the first radio access network device,the first message that includes the context identifier for the followingreason: The terminal device needs to report, to the second radio accessnetwork device, information about the cell in which the terminal deviceis currently located; or the terminal device needs the first radioaccess network device to provide a data transmission service.

Optionally, when sending the context identifier to the first radioaccess network device by using the first message, the terminal devicetruncates the context identifier according to an instruction of thefirst radio access network device, and sends only a part of the contextidentifier obtained after the truncation. This is because when thecomplete context identifier is sent, the first message may beexcessively large, and consequently the terminal device cannotsuccessfully send the first message when signal quality is relativelypoor. Therefore, to ensure that the first message can be successfullysent, the first radio access network device may instruct the terminaldevice to send only the part of the context identifier obtained afterthe truncation. For example, the context identifier is 40 bits, and thefirst radio access network device may instruct the terminal device tosend only 24 bits.

The first message may further include the PLMN information correspondingto the second radio access network device and/or the area identifiercorresponding to the second radio access network device. The PLMNinformation corresponding to the second radio access network deviceand/or the area identifier corresponding to the second radio accessnetwork device may be carried in the first message in a manner of beingincluded in the context identifier, or may be carried in the firstmessage in a manner of being independent of the context identifier.

Optionally, the terminal device obtains a PLMN corresponding to thesecond radio access network device. After moving to the cell in whichthe first radio access network device provides a service, the terminaldevice determines, based on a PLMN broadcast in the cell, the PLMNinformation of the second radio access network device. For example, thePLMN corresponding to the second radio access network device is 103,PLMNs broadcast in the cell in which the first radio access networkdevice provides a service include 101, 102, 103, and 104, and fourpieces of PLMN information respectively corresponding to the four PLMNsare 0, 1, 2, and 3. In this case, the PLMN information added to thefirst message by the terminal device is 2. Therefore, the first radioaccess network device determines that the PLMN corresponding to thesecond radio access network device is 103. In this way, the firstmessage can be simplified, and a success rate of sending the firstmessage is ensured.

Optionally, the first message further includes area identifierindication information. The area identifier indication information isused to indicate whether an area identifier corresponding to the firstradio access network device is the same as the area identifiercorresponding to the second radio access network device. In thisembodiment, the area identifier indication information indicates thatthe area identifier corresponding to the first radio access networkdevice is the same as the area identifier corresponding to the secondradio access network device. For example, the area identifiercorresponding to the second radio access network device is 1235, and thearea identifier corresponding to the first radio access network deviceis also 1235. In this case, the terminal device sets a value of the areaidentifier indication information to “same”, and sends the areaidentifier indication information to the first radio access networkdevice. The first radio access network device determines, based on thearea identifier indication information, that the area identifiercorresponding to the second radio access network device is 1235.

Optionally, the terminal device further sends the verificationinformation to the first radio access network device. The terminaldevice may send the verification information together with the firstmessage, where the verification information is used as an independentmessage. Alternatively, the terminal device may add the verificationinformation to the first message for sending. The verificationinformation is used by the second radio access network device to verifythe terminal device.

S203. The first radio access network device receives the first messagesent by the terminal device, and sends a second message to a corenetwork device, where the second message includes the contextidentifier.

After receiving the first message, the first radio access network devicedecodes the first message, to obtain information carried in the firstmessage.

Optionally, the first radio access network device determines, based onthe context identifier included in the first message, whether to requestthe terminal device to send additional information. The additionalinformation includes at least one of the area identifier correspondingto the second radio access network device, the PLMN informationcorresponding to the second radio access network device, and anotherremaining part of the context identifier obtained after the truncation.For example, the first radio access network device determines whetherthe area identifier and/or the PLMN information corresponding to thesecond radio access network device are/is stored. If the first radioaccess network device determines that the area identifier and/or thePLMN information corresponding to the second radio access network deviceare/is not stored, the first radio access network device determines thatthe area identifier and/or the PLMN information corresponding to thesecond radio access network device need/needs to be obtained. Foranother example, the first radio access network device determines, basedon the identifier of the second radio access network device, whether aninterface exists between the first radio access network device and thesecond radio access network device. If the interface does not exist, thefirst radio access network device determines that the area identifierand/or the PLMN information corresponding to the second radio accessnetwork device need/needs to be obtained. In another optional manner,when the first message further includes the area identifier indicationinformation, the first radio access network device determines that theadditional information needs to be obtained.

If the first radio access network device determines that the additionalinformation needs to be obtained, the following optional steps areperformed.

S2021. The first radio access network device sends anadditional-information request message to the terminal device.

Specifically, the additional-information request message is sent to theterminal device through a common control channel. Theadditional-information request message may include preamble allocationinformation of the terminal device. The preamble allocation informationindicates a preamble allocated by the first radio access network deviceto the terminal device. Therefore, the terminal device may send theadditional information based on the preamble allocation information.

The additional-information request message may further includeindication information. The indication information includes at least oneof PLMN request information, area identifier request information, andrequest information of the another remaining part of the contextidentifier obtained after the truncation. The terminal devicedetermines, based on the indication information, information that needsto be sent.

S2022. The terminal device receives the additional-information requestmessage, and sends the additional information to the first radio accessnetwork device based on the additional-information request message.

Specifically, the terminal device sends the preamble to the first radioaccess network device based on the preamble allocation information.Based on the preamble, the first radio access network device allocates atransmission resource to the terminal device, and sends transmissionresource information. The terminal device sends the additionalinformation by using the transmission resource. The additionalinformation may be included in a message for sending. The message thatincludes the additional information is sent to the first radio accessnetwork device through the common control channel.

Optionally, the first radio access network device combines, into thecomplete context identifier, the part of the context identifier that isobtained after the truncation and that is included in the first message,and the another remaining part of the context identifier that isobtained after the truncation and that is obtained by using theadditional information. The first radio access network device adds thecomplete context identifier to the second message.

The second message may further include the PLMN informationcorresponding to the second radio access network device and/or the areaidentifier corresponding to the second radio access network device. ThePLMN information corresponding to the second radio access network deviceand/or the area identifier corresponding to the second radio accessnetwork device may be included in the context identifier, or may beincluded in the first message and carried in the second message in amanner of being independent of the context identifier. The PLMNinformation corresponding to the second radio access network deviceand/or the area identifier corresponding to the second radio accessnetwork device may alternatively be obtained by the first radio accessnetwork device by using the additional information, and carried in thesecond message.

The area identifier corresponding to the second radio access networkdevice that is included in the second message may alternatively bedetermined by the first radio access network device based on theindication information in the first message, and carried in the secondmessage.

Optionally, the first radio access network device stores the PLMNinformation corresponding to the second radio access network deviceand/or the area identifier corresponding to the second radio accessnetwork device. The first radio access network device adds, to thesecond message, the stored PLMN information corresponding to the secondradio access network device and/or the stored area identifiercorresponding to the second radio access network device.

Optionally, the second message further includes the verificationinformation and information about a serving cell in which the firstradio access network device serves the terminal device. The informationabout the serving cell may include at least one of a physical cellidentifier (PCI) of the serving cell, a frequency band of the servingcell, and a E-UTRAN cell global identifier (ECGI) of the serving cell.The information about the serving cell and the verification informationare used by the second radio access network device to verify theterminal device.

Optionally, the second message further includes an identifier of thefirst radio access network device. Therefore, the core network devicecan determine a sender of the second message. After receiving a returnmessage, the core network device can accurately send back the returnmessage to the first radio access network device.

The second message further includes the identifier of the second radioaccess network device. The second message may include a content part anda routing information part. The identifier of the second radio accessnetwork device may be included in the routing information part of thesecond message. Therefore, the core network device may know a receiverof the second message without reading the context identifier included inthe second message.

An advantage of the foregoing actions is that the sender and/or thereceiver of the second message are/is directly marked, so that aprobability of a message forwarding failure is reduced.

It can be understood that the second message may alternatively notinclude the identifier of the first radio access network device and theidentifier of the second radio access network device, and the corenetwork device determines the sender and the receiver. In this way, whenaccuracy is ensured, message content can be simplified, transmissionefficiency can be improved, and network resources can be saved.

Optionally, the first radio access network device determines, based onthe identifier of the second radio access network device, whether aninterface exists between the first radio access network device and thesecond radio access network device. For example, the first radio accessnetwork device may determine, based on an internally stored radio accessnetwork device list, whether an interface exists. Alternatively, thefirst radio access network device determines availability of theinterface between the first radio access network device and the secondradio access network device based on an internally stored configurationparameter. When the interface does not exist between the first radioaccess network device and the second radio access network device, thefirst radio access network device sends the second message to the corenetwork device.

S204. The core network device receives the second message, and sends, tothe second radio access network device, a third message that includesthe context identifier.

Optionally, the third message further includes the PLMN informationcorresponding to the second radio access network device and/or the areaidentifier corresponding to the second radio access network device. ThePLMN information corresponding to the second radio access network deviceand/or the area identifier corresponding to the second radio accessnetwork device may be included in the context identifier, or may beincluded in the second message and carried in the third message in amanner of being independent of the context identifier.

Optionally, the third message further includes at least one of theidentifier of the first radio access network device, PLMN informationcorresponding to the first radio access network device, and the areaidentifier corresponding to the first radio access network device. Theforegoing information is used by the core network device to determinethe first radio access network device when sending a return message.

Optionally, the method may further include step S2041, to be specific,the core network device sends, to the second radio access networkdevice, the verification information of the terminal device and theinformation about the serving cell in which the first radio accessnetwork device serves the terminal device. The foregoing information maybe included in the third message for sending, or may be sent in a mannerof being independent of the third message.

S205. The second radio access network device sends context informationof the terminal device to the core network device based on the thirdmessage that includes the context identifier.

The context information of the terminal device is associated with theidentifier of the terminal device.

The context information may further include an acknowledgement message,and the acknowledgement message is used to feed back, to the first radioaccess network device, information that the second radio access networkdevice has learned of a current location of the terminal device.

The context information may further include a connection configurationparameter used for establishing an RRC connection between the terminaldevice and the first radio access network device.

Optionally, the second radio access network device further receives theverification information and the information about the serving cell inwhich the first radio access network device serves the terminal device,and verifies the terminal device based on the verification informationand the information about the serving cell, where the verificationinformation and the information about the serving cell are sent by thecore network device.

S206. The core network device sends the context information to the firstradio access network device.

Optionally, the first radio access network device determines, based onthe context information, that the second radio access network device haslearned of the current location of the terminal device.

Optionally, the first radio access network device establishes the RRCconnection to the terminal device by using the context information, andprovides a data transmission service for the terminal device.

It should be noted that steps S205 and S206 are optional steps.

In this embodiment of the present disclosure, when no availableinterface exists between the first radio access network device and thesecond radio access network device, communication between the radioaccess network devices can still be implemented by using the corenetwork device as a message transfer medium, thereby improving workingefficiency of a system.

FIG. 3 is a schematic diagram of a communication method in a wirelessnetwork according to another embodiment of the present disclosure. Inthis embodiment, as shown in FIG. 1B, the first radio access networkdevice and the second radio access network device are respectivelycontrolled by different core network devices. In this embodiment, thefirst radio access network device is controlled by a first core networkdevice, and the second radio access network device is controlled by asecond core network device. The method provided in this embodiment isdescribed in detail below from a perspective of interaction withreference to FIG. 3.

S301. The second radio access network device sends a context identifierto a terminal device.

S302. The terminal device receives the context identifier from thesecond radio access network device, and sends, to a first radio accessnetwork device, a first message that includes the context identifier.

Optionally, the first message includes indication information. Theindication information is used to indicate whether an area identifiercorresponding to the first radio access network device is the same as anarea identifier corresponding to the second radio access network device.In this embodiment, the indication information indicates that the areaidentifier corresponding to the first radio access network device isdifferent from the area identifier corresponding to the second radioaccess network device. For example, the area identifier corresponding tothe second radio access network device is 1236, and the area identifiercorresponding to the first radio access network device is 1235. In thiscase, the terminal device sets a value of the indication information to“different”, and sends the indication information to the first radioaccess network device.

S303. The first radio access network device receives the first messagesent by the terminal device, and sends a second message to the firstcore network device, where the second message includes the contextidentifier.

After receiving the first message, the first radio access network devicedecodes the first message, to obtain information carried in the firstmessage.

Optionally, the first radio access network device determines, based onthe indication information included in the first message, that the areaidentifier corresponding to the second radio access network device isdifferent from the area identifier corresponding to the first radioaccess network device. In this case, the first radio access networkdevice needs to learn of the complete area identifier corresponding tothe second radio access network device. Therefore, the first radioaccess network device performs the following steps.

S3021. The first radio access network device sends an area identifierrequest message to the terminal device.

S3022. The terminal device receives the area identifier request message,and sends, to the first radio access network device, an area identifiercorresponding to the second radio access network device.

Therefore, the first radio access network device obtains, by using theforegoing process, the area identifier corresponding to the second radioaccess network device, and adds the area identifier to the secondmessage.

S304. The first core network device receives the second message, andsends, to a second core network device, a fourth message that includesthe context identifier.

Optionally, the fourth message further includes PLMN informationcorresponding to the second radio access network device and/or the areaidentifier corresponding to the second radio access network device. ThePLMN information corresponding to the second radio access network deviceand/or the area identifier corresponding to the second radio accessnetwork device are/is included in the context identifier, or are/isincluded in the second message and carried in the fourth message in amanner of being independent of the context identifier.

The fourth message may further include an identifier of the first radioaccess network device. Therefore, after receiving a return message, thefirst core network device and the second core network device canaccurately send back the return message to the first radio accessnetwork device.

Optionally, the fourth message further includes verification informationand information about a serving cell in which the first radio accessnetwork device serves the terminal device.

S305. The second core network device receives the fourth message, andsends, to the second radio access network device, a message thatincludes the context identifier.

S306. The second radio access network device sends context informationof the terminal device to the second core network device based on themessage that includes the context identifier.

S307. The second core network device sends the context information tothe first core network device.

S308. The first core network device sends the context information to thefirst radio access network device.

It should be noted that for related content that is not described indetail in steps S301 to S308, refer to a corresponding part in stepsS201 to S206 in the method shown in FIG. 2. Details are not describedherein again. Steps S306 to S308 are optional steps.

In this embodiment of the present disclosure, when no availableinterface exists between the first radio access network device and thesecond radio access network device, communication between the radioaccess network devices can still be implemented by using respective corenetwork devices as message transfer media, thereby improving workingefficiency of a system.

The foregoing mainly describes the solutions provided in the embodimentsof the present disclosure from a perspective of interaction betweendevices. It can be understood that, to implement the foregoingfunctions, each device such as the terminal device, the access networkdevice, and the core network device includes corresponding hardwarestructures and/or software modules for executing functions. A personskilled in the art should be readily aware that, in combination with theexamples described in the embodiments disclosed in this specification,units and algorithms steps can be implemented by hardware or acombination of hardware and computer software in the present disclosure.Whether a function is performed by hardware or computer software drivinghardware depends on particular applications and design constraints ofthe technical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of the present disclosure.

FIG. 4 is a possible schematic structural diagram of the radio accessnetwork device in the foregoing embodiments. It should be noted that theradio access network device can perform the methods in the foregoingembodiments. Therefore, for specific details of the radio access networkdevice, refer to the descriptions in the foregoing embodiments. Forbrevity, same content is not described again below. The radio accessnetwork device may be the radio access network device 10 shown in FIG.1A or FIG. 1B. The radio access network device is a first radio accessnetwork device that serves a terminal device. The radio access networkdevice includes a receiving unit 401, a processing unit 402, and asending unit 403.

The receiving unit 401 is configured to receive, from a terminal device,a first message that includes a context identifier.

The processing unit 402 is configured to decode the first message thatincludes the context identifier. The context identifier includes anidentifier of a second radio access network device and an identifier ofthe terminal device that is allocated by the second radio access networkdevice.

The sending unit 403 is configured to send a second message to a corenetwork device. The second message includes the context identifier.

The receiving unit 401 is further configured to receive contextinformation of the terminal device from the core network device. Thecontext information of the terminal device is associated with theidentifier of the terminal device.

The terminal device is configured to: truncate the context identifierbased on an instruction of the radio access network device, and sendonly a part that is of the context identifier and that is obtained afterthe truncation.

Optionally, the processing unit 402 is further configured to decode thecontext identifier, to obtain PLMN information corresponding to thesecond radio access network device and/or an area identifiercorresponding to the second radio access network device that are/isincluded in the context identifier. The area identifier may be a TAC, anRAC, or an LAC.

The processing unit 402 may be further configured to decode the firstmessage, to obtain the PLMN information corresponding to the secondradio access network device and/or the area identifier corresponding tothe second radio access network device that are/is included in the firstmessage. Same as that described in step S202 shown in FIG. 2, the PLMNinformation corresponding to the second radio access network deviceand/or the area identifier corresponding to the second radio accessnetwork device may be carried in the first message in a manner of beingincluded in the context identifier, or may be carried in the firstmessage in a manner of being independent of the context identifier.

Optionally, the processing unit 402 is further configured to obtain, bydecoding the first message, the PLMN information corresponding to thesecond radio access network device. Specifically, the processing unit402 may obtain, by using the method described in step S202 shown in FIG.2, a PLMN corresponding to the second radio access network device.Details are not described herein again.

Optionally, the processing unit 402 is further configured to obtainindication information by decoding the first message. The indicationinformation indicates whether an area identifier corresponding to thefirst radio access network device is the same as the area identifiercorresponding to the second radio access network device. If theindication information indicates that the area identifier correspondingto the first radio access network device is the same as the areaidentifier corresponding to the second radio access network device, theprocessing unit 402 determines that the area identifier corresponding tothe second radio access network device is an area identifiercorresponding to a current radio access network device. If theindication information indicates that the area identifier correspondingto the first radio access network device is different from the areaidentifier corresponding to the second radio access network device, theprocessing unit 402 may control execution of the following operations byusing the method described in step S303 shown in FIG. 3, to obtain thecomplete area identifier corresponding to the second radio accessnetwork device: The sending unit 403 is further configured to send anarea identifier request message to the terminal device, and thereceiving unit 401 is further configured to receive, from the terminaldevice, the area identifier corresponding to the second radio accessnetwork device.

Optionally, the processing unit 402 is further configured to determine,based on the context identifier, whether the radio access network deviceneeds to request the terminal device to send additional information. Theadditional information includes at least one of the area identifiercorresponding to the second radio access network device, the PLMNinformation corresponding to the second radio access network device, andanother remaining part of the context identifier obtained after thetruncation. For example, the processing unit 402 may determine, bydetermining whether the area identifier and/or the PLMN informationcorresponding to the second radio access network device are/is stored,whether the additional information needs to be obtained.

If the processing unit 402 determines that the additional informationneeds to be obtained, the processing unit 402 may control execution ofthe following operations by using the method described in step S203shown in FIG. 2.

The sending unit 403 is further configured to send anadditional-information request message to the terminal device. Thesending unit 403 may send the additional-information request messagethrough a common control channel. The processing unit 402 may furtheradd preamble allocation information of the terminal device to theadditional-information request message. The preamble allocationinformation indicates a preamble allocated by the processing unit 402 tothe terminal device. The processing unit 402 may further add indicationinformation to the additional-information request message. Theindication information includes at least one of PLMN requestinformation, area identifier request information, and requestinformation of the another remaining part of the context identifierobtained after the truncation.

The receiving unit 401 is further configured to receive, from theterminal device, a message that includes the additional information.Optionally, the receiving unit 401 is further configured to receive thepreamble sent by the terminal device. The processing unit 402 is furtherconfigured to: allocate a transmission resource to the terminal devicebased on the preamble, and control the sending unit 403 to sendinformation about the transmission resource to the terminal device. Thereceiving unit 401 is further configured to receive the additionalinformation from the terminal device.

The processing unit 402 is further configured to: combine, into thecomplete context identifier, the part of the context identifier that isobtained after the truncation and that is included in the first message,and the another remaining part of the context identifier that isobtained after the truncation and that is obtained by using theadditional information, and add the complete context identifier to thesecond message.

The processing unit 402 may be further configured to add, to the secondmessage, the PLMN information corresponding to the second radio accessnetwork device and/or the area identifier corresponding to the secondradio access network device, and the sending unit 403 sends the secondmessage to the core network device.

Optionally, the processing unit 402 is further configured to add, to thesecond message, the stored PLMN information corresponding to the secondradio access network device and/or the stored area identifiercorresponding to the second radio access network device.

Optionally, the processing unit 402 is further configured to add anidentifier of the radio access network device to the second message.

Optionally, the processing unit 402 is further configured to add theidentifier of the second radio access network device to a routinginformation part of the second message.

The receiving unit 401 is further configured to receive verificationinformation from the terminal device, and the processing unit 402 isfurther configured to add, to the second message, the verificationinformation and information about a serving cell in which the radioaccess network device serves the terminal device. The information aboutthe serving cell includes at least one of a physical cell identifier ofthe serving cell, a frequency band of the serving cell, and a cellglobal identifier of the serving cell.

Optionally, the processing unit 402 is further configured to determine,based on the identifier of the second radio access network device,whether an interface exists between the radio access network device andthe second radio access network device. If the interface does not exist,the processing unit 402 controls the sending unit 403 to send the secondmessage to the core network device.

The processing unit 402 may be further configured to decode the contextinformation of the terminal device that is received from the corenetwork device. The processing unit 402 may obtain an acknowledgementmessage from the context information. The acknowledgement message isused to feed back information that the second radio access networkdevice has learned of a current location of the terminal device.Alternatively, the processing unit 402 may obtain, from the contextinformation, a connection configuration parameter used to establish anRRC connection to the terminal device, so that the radio access networkdevice can provide a data transmission service for the terminal device.

Other implementable functions of the foregoing units not described indetail are the same as related functions in the communication methods ina wireless network shown in FIG. 2 and FIG. 3. Details are not describedherein again. Through collaborative cooperation between the foregoingunits, when no available interface exists between the radio accessnetwork device and the second radio access network device, timely andeffective communication can still be implemented by using the corenetwork device as a message transfer medium, thereby improving workingefficiency.

Functions of the units in the radio access network device may beimplemented by using hardware, or may be implemented by executingcorresponding software by hardware. For example, the foregoing units maybe hardware that has a function of executing various modules, or may beanother hardware device that can execute a corresponding computerprogram to complete the foregoing functions.

FIG. 5 is a possible schematic structural diagram of the radio accessnetwork device in the foregoing embodiments. The radio access networkdevice includes a receiver 501, a processor 502, and a transmitter 503.The processing unit 402 described in FIG. 4 may be implemented by usingthe processor 502, the receiving unit 401 and the sending unit 403 maybe respectively implemented by using the receiver 501 and thetransmitter 503, and the receiver 501 and the transmitter 503 may beconfigured to support the radio access network device in receiving datafrom and sending data to the terminal device and the core network devicein the foregoing embodiments. The radio access network device mayfurther include a memory 504 that may be configured to store programcode and data of the radio access network device. Components in theradio access network device are coupled together, and are configured tosupport various functions of the radio access network device in thecommunication methods in the embodiments described in FIG. 2 and FIG. 3.

FIG. 6 is another possible schematic structural diagram of the radioaccess network device in the foregoing embodiments. It should be notedthat the radio access network device can perform the methods in theforegoing embodiments. Therefore, for specific details of the radioaccess network device, refer to the descriptions in the foregoingembodiments. For brevity, same content is not described again below. Theradio access network device may be the radio access network device 20shown in FIG. 1A or FIG. 1B. The radio access network device may be aradio access network device that instructs a terminal device to enter alight connection mode. The radio access network device includes aprocessing unit 601, a sending unit 602, and a receiving unit 603.

The processing unit 601 is configured to allocate an identifier of aterminal device to the terminal device.

The sending unit 602 is configured to send a context identifier to theterminal device. The context identifier includes an identifier of theradio access network device and the identifier of the terminal device.

The receiving unit 603 is configured to receive, from a core networkdevice, a message that includes the context identifier.

The processing unit 601 is further configured to determine contextinformation of the terminal device in response to the message thatincludes the context identifier. The context information of the terminaldevice is associated with the identifier of the terminal device.

The sending unit 602 is further configured to send the contextinformation of the terminal device to the core network device.

The processing unit 601 may be configured to combine, by using themethod described in step S201 in FIG. 2, the identifier of the radioaccess network device and the identifier of the terminal device intocontinuous character strings, to form the context identifier. Theprocessing unit 601 may be alternatively configured to combine theidentifier of the radio access network device and the identifier of theterminal device into discontinuous character strings, to form thecontext identifier.

Optionally, the processing unit 601 is further configured to add, to thecontext identifier by using the method described in step S201 in FIG. 2,PLMN information corresponding to the radio access network device and/oran area identifier corresponding to the radio access network device.

The processing unit 601 may be further configured to decode the messagethat includes the context identifier and that is received by thereceiving unit 603 from the core network device. The message furtherincludes the PLMN information corresponding to the radio access networkdevice and/or the area identifier corresponding to the radio accessnetwork device.

The processing unit 601 may be further configured to decode the messagethat includes the context identifier and that is received by thereceiving unit 603 from the core network device. The message furtherincludes at least one of an identifier of a first radio access networkdevice, PLMN information corresponding to the first radio access networkdevice, and an area identifier corresponding to the first radio accessnetwork device. The first radio access network device is a radio accessnetwork device that serves the terminal device.

The receiving unit 603 may be further configured to receive, from thecore network device, verification information of the terminal device andinformation about a serving cell in which the first radio access networkdevice serves the terminal device. The information about the servingcell includes at least one of a physical cell identifier of the servingcell, a frequency band of the serving cell, and a cell global identifierof the serving cell.

The processing unit 601 may be further configured to verify the terminaldevice based on the verification information and the information aboutthe serving cell that are received by the receiving unit 603.

Optionally, before the receiving unit 603 receives, from the corenetwork device, the message that includes the context identifier, thesending unit 602 is further configured to send control information tothe terminal device. The control information is used to instruct theterminal device to enter a light connection mode.

Functions of the units in the radio access network device may beimplemented by using hardware, or may be implemented by executingcorresponding software by hardware. For example, the foregoing units maybe hardware that has a function of executing various modules, or may beanother hardware device that can execute a corresponding computerprogram to complete the foregoing functions.

FIG. 7 is another possible schematic structural diagram of the radioaccess network device in the foregoing embodiments. The radio accessnetwork device includes a processor 701, a transmitter 702, and areceiver 703. The processing unit 601 described in FIG. 6 may beimplemented by using the processor 701, the sending unit 602 and thereceiving unit 603 may be respectively implemented by using thetransmitter 702 and the receiver 703, and the transmitter 702 and thereceiver 703 may be configured to support the radio access networkdevice in receiving data from and sending data to the terminal deviceand the core network device in the foregoing embodiments. The radioaccess network device may further include a memory 704 that may beconfigured to store program code and data of the radio access networkdevice. Components in the radio access network device are coupledtogether, and are configured to support various functions of the radioaccess network device in the communication methods in the embodimentsdescribed in FIG. 2 and FIG. 3.

It may be understood that FIG. 5 and FIG. 7 show only simplified designsof the radio access network devices. In actual application, the radioaccess network device may include any quantity of transmitters,receivers, processors, memories, and the like, and all radio accessnetwork devices that can implement the embodiments of the presentdisclosure fall within the protection scope of the present disclosure.

FIG. 8 is a possible schematic structural diagram of the terminal devicein the foregoing embodiments. It should be noted that the terminaldevice can perform the methods in the foregoing embodiments. Therefore,for specific details of the terminal device, refer to the descriptionsin the foregoing embodiments. For brevity, same content is not describedagain below. The terminal device may be the terminal device 30 shown inFIG. 1A or FIG. 1B. The terminal device includes a receiving unit 801, aprocessing unit 802, and a sending unit 803.

The receiving unit 801 is configured to receive a context identifierfrom a second radio access network device.

The processing unit 802 is configured to decode the context identifier.The context identifier includes an identifier of the second radio accessnetwork device and an identifier of the terminal device that isallocated by the second radio access network device.

The sending unit 803 is configured to send a first message to a firstradio access network device. The first message includes the contextidentifier.

Optionally, the processing unit 802 is further configured to truncatethe context identifier according to an instruction of the first radioaccess network device by using the method described in step S202 shownin FIG. 2, to control the sending unit 803 to send only a part of thecontext identifier obtained after the truncation.

The processing unit 802 may be further configured to add, to the firstmessage, PLMN information corresponding to the second radio accessnetwork device and/or an area identifier corresponding to the secondradio access network device. Same as that described in step S202 shownin FIG. 2, the PLMN information corresponding to the second radio accessnetwork device and/or the area identifier corresponding to the secondradio access network device may be carried in the first message in amanner of being included in the context identifier, or may be carried inthe first message in a manner of being independent of the contextidentifier.

Optionally, the processing unit 802 is further configured to determine,by using the method described in step S202 in the method shown in FIG.2, the PLMN information of the second radio access network device thatis carried in the first message. Specifically, the processing unit 802determines, based on a recorded PLMN corresponding to the second radioaccess network device and a PLMN that is broadcast in a cell in whichthe first radio access network device provides a service and that isreceived by the receiving unit 801, the PLMN information correspondingto the second radio access network device.

Optionally, before the sending unit 803 sends the first message, thereceiving unit 801 is further configured to receive the second areaidentifier of the second radio access network device and a first areaidentifier of the first radio access network device. The processing unit802 is further configured to: determine whether the second areaidentifier is the same as the first area identifier, and add, to thefirst message, area identifier indication information that indicateswhether the first area identifier is the same as the second areaidentifier.

Optionally, as described in the methods shown in FIG. 2 and FIG. 3, ifthe processing unit 802 determines that the second area identifier isdifferent from the first area identifier, the receiving unit 801 isfurther configured to receive an area identifier request message fromthe first radio access network device. The processing unit 802 isfurther configured to: respond to the area identifier request message,and control the sending unit 803 to send the second area identifier tothe first radio access network device.

Optionally, as described in the method in FIG. 2, the receiving unit 801is further configured to receive an additional-information requestmessage sent by the first radio access network device. The processingunit 802 is further configured to decode the additional-informationrequest message, to obtain preamble allocation information carried inthe additional-information request message. The processing unit 802 isfurther configured to obtain indication information included in theadditional-information request message. The indication informationincludes at least one of PLMN request information, area identifierrequest information, and request information of the remaining part ofthe context identifier obtained after the truncation. The processingunit 802 is further configured to determine, based on the indicationinformation, information that needs to be sent.

The sending unit 803 may be further configured to send a preamble to thefirst radio access network device based on the preamble allocationinformation. The receiving unit 801 is further configured to receive,from the first radio access network device, information about anallocated transmission resource. The sending unit 803 is furtherconfigured to send additional information to the first radio accessnetwork device by using the transmission resource. The sending unit 803may send the additional information through a common control channel.

The receiving unit 801 may be further configured to receive controlinformation from the second radio access network device. The processingunit 802 is further configured to: respond to the control information,and control the terminal device to enter a light connection mode.

The sending unit 803 may be further configured to send verificationinformation of the terminal device to the first radio access networkdevice.

Other implementable functions of the foregoing units not described indetail are the same as related functions in the communication methods ina wireless network shown in FIG. 2 and FIG. 3. Details are not describedherein again. Through collaborative cooperation between the foregoingunits, the terminal device can send, to the first radio access networkdevice, the PLMN information corresponding to the second radio accessnetwork device and/or the area identifier corresponding to the secondradio access network device when occupying as few transmission resourcesas possible.

Functions of the units in the terminal device may be implemented byusing hardware, or may be implemented by executing correspondingsoftware by hardware. For example, the foregoing units may be hardwarethat has a function of executing various modules, or may be anotherhardware device that can execute a corresponding computer program tocomplete the foregoing functions.

FIG. 9 is a possible schematic structural diagram of the terminal devicein the foregoing embodiments. The terminal device includes a receiver901, a processor 902, and a transmitter 903. The receiving unit 801 andthe sending unit 803 described in FIG. 8 may be implemented by using thereceiver 901 and the transmitter 903, and the processing unit 802 may beimplemented by using the processor 902. The receiver 901 and thetransmitter 903 may be configured to support the terminal device inreceiving data from and sending data to the first radio access networkdevice and the second radio access network device in the foregoingembodiments. The terminal device may further include a memory 904 thatmay be configured to store program code and data of the terminal device.Components in the terminal device are coupled together, and areconfigured to support various functions of the terminal device in thecommunication methods in the embodiments described in FIG. 2 and FIG. 3.

It may be understood that FIG. 9 shows only a simplified design of theterminal device. In actual application, the terminal device may includeany quantity of transmitters, receivers, processors, memories, and thelike, and all terminal devices that can implement the embodiments of thepresent disclosure fall within the protection scope of the presentdisclosure.

FIG. 10 is a possible schematic structural diagram of the core networkdevice in the foregoing embodiments. It should be noted that the corenetwork device can perform the methods in the foregoing embodiments.Therefore, for specific details of the core network device, refer to thedescriptions in the foregoing embodiments. For brevity, same content isnot described again below. The core network device may be the corenetwork device 1 shown in FIG. 1A or FIG. 1B. The core network deviceincludes a receiving unit 1001, a processing unit 1002, and a sendingunit 1003.

The receiving unit 1001 is configured to receive a second message from afirst radio access network device.

The processing unit 1002 is configured to decode the second message. Thesecond message includes a context identifier of a terminal device, andthe context identifier includes an identifier of a second radio accessnetwork device and an identifier of the terminal device that isallocated by the second radio access network device.

The sending unit 1003 is configured to send a third message to a secondcore network device or the second radio access network device. The thirdmessage includes the context identifier.

The receiving unit 1001 is further configured to receive contextinformation of the terminal device from the second core network deviceor the second radio access network device. The context information isassociated with the identifier of the terminal device.

The sending unit 1001 is further configured to send the contextinformation to the first radio access network device.

Optionally, the processing unit 1002 is further configured to obtain, bydecoding the second message, PLMN information corresponding to thesecond radio access network device and/or an area identifiercorresponding to the second radio access network device that are/iscarried in the second message. The PLMN information corresponding to thesecond radio access network device and/or the area identifiercorresponding to the second radio access network device may be carriedin the second message in a manner of being included in the contextidentifier, or may be carried in the second message in a manner of beingindependent of the context identifier.

The processing unit 1002 may be further configured to obtain, bydecoding the second message, verification information and informationabout a serving cell in which the first radio access network deviceserves the terminal device, where the verification information and theinformation about the serving cell are carried in the second message.The information about the serving cell includes at least one of aphysical cell identifier of the serving cell, a frequency band of theserving cell, and a cell global identifier of the serving cell.

The processing unit 1002 may be further configured to obtain, bydecoding the second message, an identifier of the first radio accessnetwork device that is carried in the second message.

Optionally, the processing unit 1002 is further configured to add, tothe third message, the PLMN information corresponding to the secondradio access network device and/or the area identifier corresponding tothe second radio access network device. The PLMN informationcorresponding to the second radio access network device and/or the areaidentifier corresponding to the second radio access network device maybe carried in the third message in a manner of being included in thecontext identifier, or may be carried in the third message in a mannerof being independent of the context identifier.

The processing unit 1002 may be further configured to add, to the thirdmessage, the verification information and the information about theserving cell in which the first radio access network device serves theterminal device.

The processing unit 1002 is further configured to add, to the thirdmessage, at least one of the identifier of the first radio accessnetwork device, PLMN information corresponding to the first radio accessnetwork device, and an area identifier corresponding to the first radioaccess network device.

Other implementable functions of the foregoing units not described indetail are the same as related functions in the communication methods ina wireless network shown in FIG. 2 and FIG. 3. Details are not describedherein again. Through collaborative cooperation between the foregoingunits, the core network device may be used as a message transfer medium,to implement timely and effective communication between the first radioaccess network device and the second radio access network device,thereby improving working efficiency.

Functions of the units in the core network device may be implemented byusing hardware, or may be implemented by executing correspondingsoftware by hardware. For example, the foregoing units may be hardwarethat has a function of executing various modules, or may be anotherhardware device that can execute a corresponding computer program tocomplete the foregoing functions.

FIG. 11 is a possible schematic structural diagram of the core networkdevice in the foregoing embodiments. The core network device includes areceiver 1101, a processor 1102, and a transmitter 1103. The processingunit 1002 described in FIG. 10 may be implemented by using the processor1102, the receiving unit 1001 and the sending unit 1003 may berespectively implemented by using the receiver 1101 and the transmitter1103, and the receiver 1101 and the transmitter 1103 may be configuredto support the core network device in receiving data from and sendingdata to the radio access network devices in the foregoing embodiments.The core network device may further include a memory 1104 that may beconfigured to store program code and data of the core network device.Components in the core network device are coupled together, and areconfigured to support various functions of the core network device inthe communication methods in the embodiments described in FIG. 2 andFIG. 3.

FIG. 12 is another possible schematic structural diagram of the corenetwork device in the foregoing embodiments. It should be noted that thecore network device can perform the methods in the foregoingembodiments. Therefore, for specific details of the core network device,refer to the descriptions in the foregoing embodiments. For brevity,same content is not described again below. The core network device maybe the core network device 2 shown in FIG. 1B. The core network deviceincludes a receiving unit 1201, a processing unit 1202, and a sendingunit 1203.

The receiving unit 1201 is configured to receive a fourth message from afirst radio access network device or a first core network device.

The processing unit 1202 is configured to decode the fourth message. Thefourth message includes a context identifier of a terminal device, andthe context identifier includes an identifier of a second radio accessnetwork device and an identifier of the terminal device that isallocated by the second radio access network device.

The sending unit 1203 is configured to send, to the second radio accessnetwork device, a message that includes the context identifier.

The receiving unit 1201 is further configured to receive contextinformation of the terminal device from the second radio access networkdevice. The context information of the terminal device is associatedwith the identifier of the terminal device.

The sending unit 1203 is further configured to send the contextinformation to the first radio access network device or the first corenetwork device.

Optionally, the processing unit 1202 is further configured to obtain, bydecoding the fourth message, PLMN information corresponding to thesecond radio access network device and/or an area identifiercorresponding to the second radio access network device that are/iscarried in the fourth message. The PLMN information corresponding to thesecond radio access network device and/or the area identifiercorresponding to the second radio access network device may be carriedin the fourth message in a manner of being included in the contextidentifier, or may be carried in the fourth message in a manner of beingindependent of the context identifier.

The processing unit 1202 may be further configured to obtain, bydecoding the fourth message, an identifier of the first radio accessnetwork device that is carried in the fourth message.

The processing unit 1202 may be further configured to obtain, bydecoding the fourth message, verification information and informationabout a serving cell in which the first radio access network deviceserves the terminal device, where the verification information and theinformation about the serving cell are carried in the fourth message.The information about the serving cell includes at least one of aphysical cell identifier of the serving cell, a frequency band of theserving cell, and a cell global identifier of the serving cell.

Optionally, the processing unit 1202 is further configured to add, tothe message that includes the context identifier, at least one of theidentifier of the first radio access network device, PLMN informationcorresponding to the first radio access network device, and an areaidentifier corresponding to the first radio access network device.

Optionally, the sending unit 1203 is further configured to send, to thesecond radio access network device, the verification information of theterminal device and the information about the serving cell in which thefirst radio access network device serves the terminal device.

Other implementable functions of the foregoing units not described indetail are the same as related functions in the communication methods ina wireless network shown in FIG. 2 and FIG. 3. Details are not describedherein again. Through collaborative cooperation between the foregoingunits, the core network device may be used as a message transfer medium,to implement timely and effective communication between the first radioaccess network device and the second radio access network device,thereby improving working efficiency.

Functions of the units in the core network device may be implemented byusing hardware, or may be implemented by executing correspondingsoftware by hardware. For example, the foregoing units may be hardwarethat has a function of executing various modules, or may be anotherhardware device that can execute a corresponding computer program tocomplete the foregoing functions.

FIG. 13 is a possible schematic structural diagram of the core networkdevice in the foregoing embodiments. The core network device includes areceiver 1301, a processor 1302, and a transmitter 1303. The processingunit 1202 described in FIG. 12 may be implemented by using the processor1302, the receiving unit 1201 and the sending unit 1203 may berespectively implemented by using the receiver 1301 and the transmitter1303, and the receiver 1301 and the transmitter 1303 may be configuredto support the core network device in receiving data from and sendingdata to the radio access network devices in the foregoing embodiments.The core network device may further include a memory 1304 that may beconfigured to store program code and data of the core network device.Components in the core network device are coupled together, and areconfigured to support various functions of the core network device inthe communication methods in the embodiments described in FIG. 2 andFIG. 3.

It should be understood that FIG. 11 and FIG. 13 show only simplifieddesigns of the core network devices. In actual application, the corenetwork device may include any quantity of transmitters, receivers,processors, memories, and the like, and all core network devices thatcan implement the embodiments of the present disclosure fall within theprotection scope of the present disclosure.

A person skilled in the art may further understand that variousillustrative logical blocks and steps that are listed in the embodimentsof the present disclosure may be implemented by using electronichardware, computer software, or a combination thereof. In order toclearly demonstrate interchangeability between the hardware and thesoftware, functions of the foregoing various illustrative components andsteps have been generally described. Whether the functions areimplemented by using hardware or software depends on particularapplications and a design requirement of the entire system. A person ofordinary skill in the art may use various methods to implement thedescribed functions for each particular application, but it should notbe considered that the implementation goes beyond the protection scopeof the embodiments of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin the embodiments of the present disclosure may implement or operatethe described functions by using a general processing unit, a digitalsignal processing unit, an application-specific integrated circuit(ASIC), a field programmable gate array (FPGA) or another programmablelogical apparatus, a discrete gate or transistor logic, a discretehardware component, or a design of any combination thereof. The generalprocessing unit may be a microprocessing unit. Optionally, the generalprocessing unit may be any conventional processing unit, controller,microcontroller, or state machine. The processing unit may beimplemented by a computing apparatus combination, such as a digitalsignal processing unit and a microprocessing unit, a plurality ofmicroprocessing units, one or more microprocessing units with a digitalsignal processing unit core, or any other similar configuration.

Steps of the methods or algorithms described in the embodiments of thepresent disclosure may be directly embedded into hardware, a softwaremodule executed by a processing unit, or a combination thereof. Thesoftware module may be stored in a RAM memory, a flash memory, a ROMmemory, an EPROM memory, an EEPROM memory, a register, a hard disk, aremovable magnetic disk, a CD-ROM, or a storage medium in any other formin the art. For example, the storage medium may connect to a processingunit so that the processing unit may read information from the storagemedium and write information to the storage medium. Optionally, thestorage medium may be integrated into a processing unit. The processingunit and the storage medium may be configured in an ASIC, and the ASICmay be configured in a user terminal. Optionally, the processing unitand the storage medium may be configured in different components of theuser terminal.

In one or more example designs, the functions described in theembodiments of the present disclosure may be implemented by usinghardware, software, firmware, or any combination thereof. If thefunctions are implemented by software, these functions may be stored ina computer-readable medium or are transmitted to the computer-readablemedium in a form of one or more instructions or code. Thecomputer-readable medium includes a computer storage medium and acommunications medium that allows a computer program to move from oneplace to another. The storage medium may be an available medium that canbe accessed by any general-purpose or special computer. For example,such a computer readable medium may include but is not limited to a RAM,a ROM, an EEPROM, a CD-ROM or another optical disc storage, a diskstorage or another magnetic storage apparatus, or any other medium thatmay be used to bear or store program code, where the program code is ina form of an instruction or a data structure or in a form that can beread by a general-purpose or special computer or a general-purpose orspecial processing unit. In addition, any connection may beappropriately defined as a computer-readable medium. For example, ifsoftware is transmitted from a website, a server, or another remoteresource through a coaxial cable, an optical fiber computer, a twistedpair, a digital subscriber line (DSL), or in a wireless manner, such asinfrared, radio, or microwave, the software is included in the definedcomputer-readable medium. The disk and the disc include a compresseddisk, a laser disk, an optical disc, a DVD, a floppy disk, and a Blu-raydisc. The disk generally copies data by a magnetic means, and the discgenerally copies data optically by a laser means. The foregoingcombination may also be included in the computer-readable medium.

According to the foregoing description of this specification in thepresent disclosure, technologies in the art may use or implement thecontent of the present disclosure. Any modification based on thedisclosed content shall be considered obvious in the art. The basicprinciples described in the present disclosure may be applied to othervariations without departing from the essence and scope of the presentdisclosure. Therefore, the content disclosed in the present disclosureis not limited to the described embodiments and designs but may also beextended to a maximum scope that is consistent with the principles anddisclosed new features of the present disclosure.

What is claimed is:
 1. A radio access network device, comprising: astorage medium including executable instructions; and a processor;wherein the executable instructions, when executed by the processor,cause the radio access network device to: receive, from a terminaldevice, a first message that comprises a part of a context identifierthat is obtained after a truncation; determine, based on the firstmessage, whether a remaining part of the context identifier needs to beobtained, wherein the remaining part of the context identifier isobtained after the truncation; in response to determining that theremaining part of the context identifier needs to be obtained, send arequest message for the remaining part of the context identifier to theterminal device; receive, from the terminal device, a third message thatcomprises the remaining part of the context identifier; send a secondmessage to a core network device, wherein the second message comprisesthe context identifier; and receive context information of the terminaldevice from the core network device.
 2. The radio access network deviceaccording to claim 1, wherein the second message further comprises anidentifier of the radio access network device.
 3. The radio accessnetwork device according to claim 1, wherein the executableinstructions, when executed by the processor, further cause the radioaccess network device to: receive verification information from theterminal device; wherein the second message further comprises theverification information and information about a serving cell in whichthe radio access network device serves the terminal device.
 4. A method,comprising: receiving, by a radio access network device from a terminaldevice, a first message that comprises a part of a context identifierthat is obtained after a truncation; determining, by the radio accessnetwork device based on the first message, whether a remaining part ofthe context identifier needs to be obtained, wherein the remaining partof the context identifier is obtained after the truncation; and inresponse to determining that the remaining part of the contextidentifier needs to be obtained, sending, by the radio access networkdevice, a request message for the remaining part of the contextidentifier to the terminal device; receiving, by the radio accessnetwork device from the terminal device, a third message that comprisesthe remaining part of the context identifier; sending, by the radioaccess network device, a second message to a core network device,wherein the second message comprises the context identifier; andreceiving, by the radio access network device, context information ofthe terminal device from the core network device.
 5. The methodaccording to claim 4, wherein the second message further comprises anidentifier of the radio access network device.
 6. The method accordingto claim 4, further comprising: receiving, by the radio access networkdevice, verification information from the terminal device; wherein thesecond message further comprises the verification information andinformation about a serving cell in which the radio access networkdevice serves the terminal device.
 7. A terminal device, comprising: astorage medium including executable instructions; and a processor;wherein the executable instructions, when executed by the processor,cause the terminal device to: transmit a first message that comprises apart of a context identifier to a radio access network device, whereinthe part of the context identifier is obtained after a truncation;receive a request message for a remaining part of the context identifierfrom the radio access network device, wherein the radio access networkdevice determines, based on the first message, whether a remaining partof the context identifier needs to be obtained, and wherein theremaining part of the context identifier is obtained after thetruncation; and transmit, in response to the request message, a thirdmessage that comprises the remaining part of the context identifier tothe radio access network device.
 8. A method, comprising: transmitting,by a terminal device, a first message that comprises a part of a contextidentifier to a radio access network device, wherein the part of thecontext identifier is obtained after a truncation; receiving, by theterminal device, a request message for a remaining part of the contextidentifier from the radio access network device, wherein the radioaccess network device determines, based on the first message, whether aremaining part of the context identifier needs to be obtained, andwherein the remaining part of the context identifier is obtained afterthe truncation; and transmitting, by the terminal device, in response tothe request message, a third message that comprises the remaining partof the context identifier to the radio access network device.